1. Field of the Invention
The present invention relates to a fiber reinforced thermoplastic resin shaped article and a method for preparing said article. The article of the present invention has excellent strength reinforced by fibers and a light weight feature, has a rib, a boss or any other projection and is suitably utilized as a vehicle part and the like.
2. Description of Related Art
One of known methods for preparing a fiber reinforced resin shaped article comprises heating and pressing a fiber reinforced thermoplastic resin sheet to prepare a product. Depending on the reinforcing fiber, this method is classified into two types. One type comprises mixing monofilaments each having a medium fiber length of from several millimeters to 100 mm with thermoplastic resin powder under a wet or dry condition, forming a fiber reinforced thermoplastic resin sheet by a heating roll press, preheating the sheet and then pressing the sheet to obtain a fiber reinforced thermoplastic resin shaped article (cf., for example, U.S. Pat. No. 4,645,565 corresponding to Japanese Patent Kokai Publication No. 28135/1982). The other type comprises extruding a molten thermoplastic resin on a mat consisting of long fibers, laminating them, forming a fiber reinforced thermoplastic resin sheet through rollers, and preheating and pressing the sheet to obtain a fiber reinforced thermoplastic resin shaped article.
When the fiber reinforced thermoplastic resin sheet is preheated to press it, the sheet expands in a thickness direction. The sheet is supplied between upper and lower molds, a clamp clearance is set to a distance greater than a thickness of the unheated reinforced thermoplastic resin sheet and the sheet is pressurized and cooled to obtain a shaped article having a larger thickness than that of the unheated fiber reinforced thermoplastic resin sheet, namely a shaped article having a larger volume than that of the unheated fiber reinforced thermoplastic resin sheet. Hereinafter, this is referred to as "expansion shaping". U.S. Pat. No. 4,670,331 (corresponding to Japanese Patent Kokai Publication No. 179234/1985) discloses a method comprising conducting the expansion shaping in this way to obtain a fiber reinforced thermoplastic resin shaped article having a large volume and a light weight.
In the expansion shaping, a flat sheet made of a fiber reinforced thermoplastic resin is preheated, and supplied and pressurized between upper and lower molds to form a sheet having a larger thickness than that of the original unpreheated fiber reinforced thermoplastic resin sheet. Accordingly, even if a recess is provided in the mold to give a rib, a boss or any other projection to the sheet, the preheated fiber reinforced thermoplastic resin sheet is merely pressurized mainly in a sheet thickness direction between the molds, and the sheet does not flow along a mold surface so that the recess is never or insufficiently filled with the fiber reinforced thermoplastic resin sheet. Accordingly, it is difficult to mold a fiber reinforced thermoplastic resin shaped article having a rib, a boss or any other projection.